Questions about goddess arc

I just have a one go reading to chapter 187 and I love all the goddess.

It seem that the logo of the school hold some meaning to the story and when I hear about the 6 virtues that the wheat of Demeter represent, I immediately think of our 6 goddess. However, they are Jupiter's goddesses so basically they are Goddesses of Zeus. I really wonder what meaning does Demeter hold in this story?

Also, something Tenri said to Diana really make me curious T.T I would guess it about some fact in the past when the Weiss escape ( I call it the destiny day of Tenri and Keima XD). What do you guys think?